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It is widely accepted that humanity is causing long-term irreversible damage to the planet. Recent scientific studies by groups such as the Netherlands Environmental Assessment Agency and the Royal Society confirm that the climate system and many of the world’s vital ecosystems are in danger. There are also serious concerns about water, food, and energy scarcity; it is not at all clear how the world will satisfy the needs of a population that will plateau at nine billion by 2050. Doing so, and doing so sustainably, should be the core objective of international environmentalism. Yet countries have not committed to sustainability as a goal, let alone agreed on the proper policies to achieve it and the appropriate distribution of its costs.

In the absence of such a consensus, the Rio+20 Conference -- a high-level diplomatic summit held in Rio de Janeiro this past June -- sought to develop ways to both accelerate sustainable technological change and alleviate poverty. The conference was part of a longer-term project, which started with the 1972 United Nations Conference on the Human Environment (UNCHE), aimed at updating the post–World War II multilateral order. That order was designed to promote widespread economic prosperity and maintain the modern welfare state. But it neglected sustainability. So, at least in the environmental realm, global summits since the first UNCHE have focused on making governments responsible for preventing irreversible and excessive environmental harm in their pursuit of prosperity.

The global UN summits on sustainable development held in 1992 and 2002 broadened the focus of the sustainability project from basic international environmental protection to the interconnections between the environment, economic development, and justice. Further, whereas the 1972 and 1992 conferences worked to create institutions and treaties, the 2002 meeting focused on promoting partnerships between the public and private sectors. The collective achievements of the UN summits of the last few decades are notable. Oil pollution in the oceans has been greatly reduced, chemical pollution on land has plummeted, stratospheric ozone depletion has been effectively addressed, safe drinking